Rotordynamics_with_ANSYS_Mechanical_Solutions

©2008ANSYS,Inc.Allrightsreserved.1ANSYS,Inc.ProprietaryRotordynamicswithANSYSMechanicalSolutionsPierreTHIEFFRYProductManagerANSYS,Inc.©2008ANSYS,Inc.Allrightsreserved.2ANSYS,Inc.ProprietaryAgenda•Generalfeatures•Generalizedaxisymmetricelement•RotordynamicswithANSYSWorkbench–AnANSYSV12.0example–Futureplans©2008ANSYS,Inc.Allrightsreserved.3ANSYS,Inc.ProprietaryGeneralfeatures©2008ANSYS,Inc.Allrightsreserved.4ANSYS,Inc.ProprietaryRotordynamicsfeatures•Pre-processing:–Appropriateelementformulationforallgeometries–Gyroscopicmomentsgeneratedbyrotatingparts–Bearings–Rotorimbalanceandotherexcitationforces(synchronousandasynchronous)–Rotationalvelocities–Structuraldamping•Solution:–Complexeigensolverformodalanalysis–Harmonicanalysis–Transientanalysis©2008ANSYS,Inc.Allrightsreserved.5ANSYS,Inc.ProprietaryRotordynamicsfeatures•Post-processing–Campbelldiagrams–Orbitplots–Modeanimation–Transientplotsandanimations•User’sguide•Advancedfeatures:–ComponentModeSynthesisforstaticparts©2008ANSYS,Inc.Allrightsreserved.6ANSYS,Inc.ProprietaryAppropriateelementformulation•Thefollowingelementsaresupportedforrotordynamicsanalysis(stationaryreferenceframe):MassMASS21BeamBEAM4,PIPE16BEAM188,BEAM189PIPE288/289SolidSOLID45,SOLID95SOLID185,SOLID186,SOLID187ShellSHELL63SHELL181,SHELL281GeneralaxisymmetricelementsSOLID272,SOLID273NewinANSYS12.0NewinANSYS12.0©2008ANSYS,Inc.Allrightsreserved.7ANSYS,Inc.ProprietaryGeneralizedaxisymmetricelement•Thenew272/273elements:•Arecomputationallyefficientwhencomparedto3Dsolid•Support3Dnon-axisymmetricloading•Allowaveryfastsetupofaxisymmetric3Dparts:•Sliceanaxisymmetric3DCADgeometrytogetplanarmodel•Meshwith272/273elements•Noneedtocalculateequivalentbeamsections•Canbecombinedwithfull3Dmodels,includingcontact2Daxisymmetricmesh3Drepresentation3Dresults(notnecessarilyaxisymmetric)©2008ANSYS,Inc.Allrightsreserved.8ANSYS,Inc.ProprietaryBearings•2Dspring/damperwithcross-couplingterms:–Realconstantsarestiffnessanddampingcoefficientsandcanvarywithspinvelocityw•Bearingelementchoicedependson:–Shape(1D,2D,3D)–Crossterms–NonlinearitiesDescriptionStiffnessandDampingcrosstermsNonlinearstiffnessanddampingcharacteristicsCOMBIN14Uniaxialspring/damperNoNoCOMBI2142-Dspring/damperUnsymmetricFunctionoftherotationalvelocityMATRIX27GeneralstiffnessordampingmatrixUnsymmetricNoMPC184MultipointconstraintelementSymmetricforlinearcharacteristics-NonefornonlinearcharacteristicsFunctionofthedisplacement©2008ANSYS,Inc.Allrightsreserved.9ANSYS,Inc.ProprietaryImbalanceandotherexcitationforces•Possibleexcitationscausedbyrotationvelocityware:–Unbalance(w)–Couplingmisalignment(2*w)–Blade,vane,nozzle,diffusers(s*w)–Aerodynamicexcitationsasincentrifugalcompressors(0.5*w)•InputmadeasaforceonthemodelyFzF202bFmrFwwzymtwr©2008ANSYS,Inc.Allrightsreserved.10ANSYS,Inc.ProprietaryRotatingdamping•Considerediftherotatingstructurehas:•structuraldamping(MP,DAMPorBETAD)•oralocalizedrotatingviscousdamper(bearing)•Thedampingforcescaninduceunstablevibrations.•TherotatingdampingeffectisactivatedalongwiththeCorioliseffect(CORIOLIScommand).DamperCOMBI214BeamBEAM4,PIPE16BEAM188,BEAM189SolidSOLID45,SOLID95SOLID185,SOLID186,SOLID187GeneralaxisymmetricSOLID272,SOLID273(newinV12.0)Elementssupportingrotatingdamping©2008ANSYS,Inc.Allrightsreserved.11ANSYS,Inc.ProprietaryCampbelldiagrams&whirl•Variationoftherotornaturalfrequencieswithrespecttorotorspeedw•Inmodalanalysisperformmultipleloadstepsatdifferentangularvelocitiesw•Asfrequenciessplitwithincreasingspinvelocity,ANSYSidentifies:–forward(FW)andbackward(BW)whirl–stable/unstableoperation–criticalspeeds•Alsoavailableformultispoolmodels©2008ANSYS,Inc.Allrightsreserved.12ANSYS,Inc.ProprietaryOrbitplots•Inaplaneperpendiculartothespinaxis,theorbitofanodeisanellipse•Itisdefinedbythreecharacteristics:semiaxesA,Bandphaseyinalocalcoordinatesystem(x,y,z)wherexistherotationaxis•Anglejistheinitialpositionofthenodewithrespecttothemajorsemi-axisA.•OrbitplotsareavailableforbeammodelsPRINTORBITSFROMNODALSOLUTIONLOCALyAXISOFORBITSINGLOBALCOORDINATES0.0000E+000.1000E+010.0000E+00LOADSTEP=1SUBSTEP=4RFRQ=0.0000IFRQ=2.5606LOADCASE=0ORBITNODEABPSIPHIymaxzmax10.00000.00000.00000.00000.00000.000020.00000.00000.00000.00000.00000.000030.382320.382320.00000.00000.382320.3823240.707110.707110.00000.00000.707110.7071150.923010.923010.00000.00000.923010.92301©2008ANSYS,Inc.Allrightsreserved.13ANSYS,Inc.ProprietaryRotordynamicsanalysisguide•Newatrelease12.0•Providesadetaileddescriptionofcapabilities•Providesguidelinesforrotordynamicsmodelsetup©2008ANSYS,Inc.Allrightsreserved.14ANSYS,Inc.ProprietarySamplemodelsavailable©2008ANSYS,Inc.Allrightsreserved.15ANSYS,Inc.ProprietaryGeneralizedaxisymmetricelement©2008ANSYS,Inc.Allrightsreserved.16ANSYS,Inc.ProprietaryNewElementTechnologyGeneralAxi-symmetricElement:272/2733Delementsgeneratedbasedon2DmeshBoundaryconditionsappliedin3DspaceNonlinearities,NodetosurfacecontactBenefitsMultipleAxiscanbedefinedinanydirectionTakeadvantageofaxi-symmetrybutdeformationisgeneralin3D1elementinΘ(hoop)directionStruct